Friday 27 July 2012 19.34 EDT
First published on Friday 27 July 2012 19.34 EDT

Riders taking part in the pro-cycling Critical Mass event have been arrested after breaching regulations restricting their route, according to police.

A spokesman for Scotland Yard said police intervened when participants in the monthly cycling event breached regulations.

Before this evening's ride, the Critical Mass website put a call out to cyclists who were prepared to be "peacefully assertive" in the face of expected police resistance to them following their planned route.

"Most London cyclists will know about the regular monthly Critical Mass ride this evening. Many will also know that the police seem concerned about it, because of all the Olympic traffic," it stated. "It might be assumed that, as usual, the mood of Critical Mass will be to peacefully assert the right of cyclists to travel safely wherever they want in London. But in case the police – who normally leave Critical Mass alone – were to decide to intervene this month, it would be good to have lots of people prepared to be peacefully assertive."

The Metropolitan police warned the cyclists to keep moving and keep south of the Thames. It later tweeted that it was making a "large number of arrests".

Police vans headed off scores of people as they rode in formation close to the park. Some were forcibly removed from their bikes as others tried to break through a cordon.

The Met said they had made arrests but did not give a number. The arrested cyclists were detained under Section 12 of the Public Order Act.